I got my iPod Touch 4 about a month ago and so far it has not suffered from the light leak issue and I believe it is working as it should.
I guess the only thing is it comes with a stainless steel back which is prone to scratches and the front which loves to attract finger prints. So technically you would need at least a case and a screen protector in order to ensure that it remains nice.
The camera is a 0.7mp fixed focus camera and while the pictures looks good when there is sufficient lighting, it is great as a HD video camera.
The battery is definitely a mark improvement from the previous models. However, transferring pictures to the iPod Touch 4 is still a little weird. You must sync folders of pictures from iTunes and you cannot delete them manually on the iPod Touch itself. While you can drag and drop songs and videos to it.
Overall, it is a nice product.